Process for preparing organotin compounds

ABSTRACT

Provided is a facile process for preparing certain organotin compounds having alkyl and alkylamino substituents. The process provides organotin precursor compounds, for example tris(dimethylamido)isopropyl tin, in a highly pure form. As such, the products of the process are particularly useful in the deposition of high-purity tin oxide films in, for example, extreme ultraviolet light (EUV) lithography techniques used in microelectronic device manufacturing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 of U.S. ProvisionalPatent Application No. 63/143,550 filed Jan. 29, 2021, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention belongs to the field of organotin chemistry. Inparticular, it relates to a facile process for preparing certainorganotin compounds, for example tris(dimethylamido)isopropyl tin withextremely high selectivity.

BACKGROUND

Certain organotin compounds have been shown to be useful in thedeposition of highly pure tin (II) oxide in applications such as extremeultraviolet (EUV) lithography techniques used in the manufacture ofcertain microelectronic devices.

Of particular interest are organotin compounds having a combination ofalkylamino groups and alkyl groups, which are useful as liquidprecursors in the deposition of tin-containing films ontomicroelectronic device substrates. Accordingly, there is a need forimproved methodology for manufacturing such organotin compounds inhighly pure forms for use in the deposition of highly pure tin oxidefilms.

SUMMARY

Provided is a facile process for preparing certain organotin compoundshaving alkyl and alkylamino substituents. The process is especiallyuseful in those circumstances where polyalkyl by-products cannot beeffectively removed via distillation, for example dialkyl tindialkylamides versus monoalkyl-species, due to their close proximity inboiling points. The process provides organotin precursor compounds, forexample tris(dimethylamido)isopropyl tin (CAS No. 1913978-89-8), in ahighly pure form. As such, the products of the process are particularlyuseful as precursors in the deposition of tin oxide films in, forexample, extreme ultraviolet light (EUV) lithography techniques used inmicroelectronic device manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a crystal structure depiction of a compound of Formula (A-a):

FIG. 2 is a crystal structure depiction of a compound of Formula (A-d):

i.e., the bis-dimethyl amine Lewis base adduct of ethyl tin trichloride.

DETAILED DESCRIPTION

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The term “about” generally refers to a range of numbers that isconsidered equivalent to the recited value (e.g., having the samefunction or result). In many instances, the term “about” may includenumbers that are rounded to the nearest significant figure.

Numerical ranges expressed using endpoints include all numbers subsumedwithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4 and5).

In a first aspect, the invention provides a process for preparing acomposition comprising a compound of Formula (I):

wherein each R is independently chosen from a C₁-C₅ alkyl group, and R¹is chosen from a C₁-C₅ alkyl group, which comprises combining:

-   -   a) a compound of Formula R¹SnX₃, wherein X is chosen from Cl, I,        and Br,    -   b) a compound of Formula Li(R)₂N, and    -   c) a compound of Formula R₂NH, wherein the compound of Formula        R₂NH is present in a molar excess over the compound of Formula        R¹SnX₃. For example, the composition comprising the compound of        Formula (I) can be prepared by a process comprising: contacting        a compound of Formula R¹SnX₃ with a compound of Formula Li(R)₂N        and a compound of Formula R₂NH. One or more of the steps of this        process can preferably be performed under conditions that        minimize exposure of the materials and/or products to light.

The C₁-C₅ alkyl group includes straight or branched chain alkyl groups.Examples include methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl,sec-butyl, n-pentyl, isopentyl, and sec-pentyl. Each of R and R¹ hereinare independently chosen from such groups, and thus can define compoundsof Formula (I) wherein one or more groups are different from the others.Preferably, R and R¹ are independently chosen from a C₁-C₃ alkyl group.

As set forth above, the compound of Formula R₂NH (i.e., thedialkylamine) is present in a molar excess relative to compound ofFormula R¹SnX₃; in one embodiment, this molar excess is at least about0.15 molar equivalents relative to the amount of the compound of FormulaR¹SnX₃. In another embodiment, the compound of Formula R₂NH isdimethylamine and R¹ is isopropyl. In another embodiment, R¹ isisopropyl and X is chloro. In another embodiment the compound of FormulaLi(R)₂N is lithium dimethylamide, the compound of Formula R₂NH isdimethylamine, and the compound of Formula R¹SnX₃ is isopropyl-tintrichloride.

In this aspect, examples of compounds of Formula (I) include:tris(dimethyl-amido)isopropyl tin; tris(diethylamido)isopropyl tin;tris(dipropylamido)isopropyl tin; tris(methylethylamido)isopropyl tin;tris(diisopropylamido)isopropyl tin; tris(di-t-butyl-amido)isopropyltin; tris(di-n-butylamido)isopropyl tin;tris(di-sec-butylamido)isopropyl tin; tris(di-neopentylamido)isopropyltin; tris(dimethylamido)methyl tin; tris(diethylamido)methyl tin;tris(di-n-propylamido)methyl tin; tris(methylethylamido)methyl tin;tris(diisopropylamido)methyl tin; tris(di-t-butylamido)methyl tin;tris(di-n-butylamido)methyl tin; tris(di-sec-butylamido)methyl tin;tris(di-neopentylamido)methyl tin; tris(dimethylamido)ethyl tin;tris(diethylamido)ethyl tin; tris(di-n-propylamido)ethyl tin;tris(methylethylamido)ethyl tin; tris(diisopropylamido)ethyl tin;tris(di-t-butylamido)ethyl tin; tris(di-n-butylamido)ethyl tin;tris(di-sec-butylamido)ethyl tin; tris(di-neopentylamido)ethyl tin;tris(dimethylamido)n-propyl tin; tris(diethylamido)n-propyl tin;tris(di-n-propylamido)n-propyl tin; tris(methylethylamido)n-propyl tin;tris(diisopropylamido)n-propyl tin; tris(di-t-butylamido)n-propyl tin;tris(di-n-butylamido)n-propyl tin; tris(di-sec-butylamido)n-propyl tin;tris(di-neopentylamido)n-propyl tin; tris(dimethylamido)n-butyl tin;tris(diethylamido)n-butyl tin; tris(dipropylamido)n-butyl tin;tris(methylethylamido)n-butyl tin; tris(diisopropylamido)n-butyl tin;tris(di-t-butylamido)n-butyl tin; tris(di-n-butylamido)n-butyl tin;tris(di-sec-butylamido)n-butyl tin; tris(di-neopentylamido)n-butyl tin;and the like.

The compounds of Formula R¹SnX₃ can be prepared by a redistributionreaction between, for example, iPrSnPh₃ (iPr=isopropyl and Ph=phenyl)and SnCl₄. In certain embodiments, the stoichiometry can be variedbetween 1:1 and 3:1 (R¹SnPh₃:SnX₄). In one embodiment, the compound ofFormula R¹SnX₃ is distilled prior to use one or more times. In thepractice of the invention, wherein the compound of Formula R¹SnX₃ isisopropyl tin trichloride, distillation prior to use can provide areactant which is at least about 99.9% pure.

In one embodiment, the compounds of Formula R¹SnX₃ include isopropyl tintrichloride, isopropyl tin tribromide, and isopropyl tin triiodide. Inone embodiment, the compound of Formula R¹SnX₃ is isopropyl tintrichloride. Reference to isopropyl tin trichloride below will thusapply to isopropyl tin tribromide and isopropyl tin triiodide as well,along with other compounds of Formula R¹SnX₃ as defined herein. Thecompounds of Formula R¹SnX₃ may be added in the form of a solution orslurry, depending on the solvent utilized. For example, in hydrocarbonsolvents, such as hexanes, this may form a slurry; in ethers such astetrahydrofuran, these compounds may form a solution.

In the above process, the compound of Formula R₂NH is present in a molarexcess relative to the compound of Formula R¹SnX₃. In certainembodiments, this molar excess will be at least about 0.15, or at leastabout 4. In one embodiment, this molar excess can be about 2 to about10, such as from about 2 to about 8 or about 2 to about 4, relative tothe compound of Formula R¹SnX₃.

In the above process, non-polar aprotic solvents such as hexane may beutilized. The process can be conducted at reduced temperatures of about−78° C. to about 10° C. The reaction time may be anywhere from 1 to 60hours at ambient temperature (i.e., from about 17° C. to about 27° C.).The reaction mixture can be filtered and subsequently vacuum distilledto remove the solvent. A non-reactive filter aid such as diatomaceousearth (i.e., celite) can be used, although higher purity products mayresult without this filter aid due, for example, to the presencemetallic species in the filter aid. The crude product can be purifiedvia a short path distillation after filtration of any residual solids.

In one embodiment, the isopropyl tin trichloride is distilled prior touse to remove impurities. For example, the isopropyl tin trichloride maybe distilled to provide a reactant which is at least about 99.9% pure.

The lithium dimethylamide may be commercially provided or can be freshlyprepared from dimethylamine and an alkyl lithium reagent.

As noted above, the process of the invention makes it possible tosynthesize compounds of Formula (I) in very high purity, including withvery little di-alkyl impurity present. Accordingly, in another aspect,the invention provides a composition comprising a compound of Formula(I):

wherein each R is independently chosen from a C₁-C₅ alkyl group, and R¹is chosen from a C₁-C₅ alkyl group, wherein said composition comprisesless than about 0.5% by mole, of a compound of Formula (II):

As a specific embodiment, R¹ is chosen from a C₁-C₃ alkyl group such asa methyl, ethyl, n-propyl, and isopropyl (iPr) group.

In one embodiment, the composition comprising a compound of Formula (I)comprises less than about 0.1% of a compound of Formula (II). In oneembodiment, the compound of Formula (II) isbis(dimethylamido)diisopropyl tin, and the compound of Formula (I) istris(dimethylamido)isopropyl tin.

In another embodiment, the composition comprising a compound of Formula(I) comprises less than about 0.05% of a compound of Formula (II). Inone embodiment, the compound of Formula (II) isbis(dimethylamido)diisopropyl tin, and the compound of Formula (I) istris(dimethylamido)isopropyl tin.

In another embodiment, the composition comprising a compound of Formula(I) comprises less than about 0.04% of a compound of Formula (II). Inone embodiment, the compound of Formula (II) isbis(dimethylamido)diisopropyl tin, and the compound of Formula (I) istris(dimethylamido)isopropyl tin.

In another embodiment, the composition comprising a compound of Formula(I) comprises less than about 0.03% of a compound of Formula (II). Inone embodiment, the compound of Formula (II) isbis(dimethylamido)diisopropyl tin, and the compound of Formula (I) istris(dimethylamido)isopropyl tin.

In another embodiment, the composition comprising a compound of Formula(I) comprises less than about 0.02% of a compound of Formula (II). Inone embodiment, the compound of Formula (II) isbis(dimethylamido)diisopropyl tin and the compound of Formula (I) istris(dimethylamido)isopropyl tin.

As will be seen below in Example L, it is possible to reach a level ofpurity, when the compound of Formula (I) is tris(dimethylamido)isopropyltin (i.e., wherein each R is methyl and R¹ is isopropyl), such that thepresence of the undesired bis(dimethylamido)diisopropyl tin impurity(i.e., Formula (II), wherein each R is methyl, and each R¹ is isopropyl)is undetectable by routine ¹¹⁹Sn NMR analysis, such as utilizing a JEOLECZ 400 with a residence time in the NMR of about 1 h to about 10 h forquantitative data acquisition.

In the above process, it is believed that a molar excess of a compoundof Formula R₂NH compared to the compound of Formula R¹SnX₃ affords an insitu intermediate Lewis base adduct having Formula (A):

wherein each R is independently chosen from a C₁-C₅ alkyl group, R¹ ischosen from a C₁-C₅ alkyl group, and X is chosen from Cl, I, or Br. Forexample, each R and R¹ may be chosen from a C₁-C₅ alkyl group, such as amethyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, sec-butyl group.Thus, an embodiment of the invention is a process for preparing acompound of Formula (I) from a compound of Formula (A), which is formedby reaction of a compound of Formula R₂NH and a compound of FormulaR¹SnX₃ and then reacts with a compound of Formula Li(R)₂N. For thisembodiment, the compound of Formula R₂NH is in excess of the compound ofFormula R¹SnX₃.

In a specific example of the above process, it is believed that a molarexcess of dimethylamine compared to isopropyl tin trichloride, which inone embodiment is about 0.15 to about 10, affords an in situintermediate Lewis base adduct having Formula (A-a):

In a similar way, a molar excess of dimethyl amine compared to ethyl tintrichloride affords an in situ Lewis base adduct having Formula (A-d):

For example, when a molar excess of dimethylamine is utilized in thereaction, the formation of the undesired dialkyl by-product,bis(dimethylamido)diisopropyl tin, has been observed to be greatlydiminished. In this regard, reproduction of Example 1 of WO2017/066319as shown in Comparative Example 1 below, resulted in a product mixtureof the desired tris(dimethylamido)isopropyl tin along with approximately1.6 mole percent (as determined by ¹¹⁹Sn NMR integration) of theundesired bis(dimethylamido)diisopropyl tin. While not wishing to bebound by any particular mechanism, it is believed that the excessdimethylamine forms the corresponding Lewis base adduct in situ, whichupon reaction with the lithium dimethylamide, advantageously improvesthe selectivity of the reaction and thus leads to the greatly improvedpurity of the desired compound of Formula (I), such astris(dimethylamido)isopropyl tin. Additionally, when care is taken toutilize recently-prepared or purified reactants, this effect isenhanced.

As further support, Lewis base adduct (A-a) was prepared, isolated andcrystallized:

Reaction of adduct (A-a) with lithium dimethylamide affordedtris(dimethylamido)isopropyl tin in high yield and outstandingselectivity for the mono-isopropyl species, at levels of contamination(with diisopropyl species) of as low as about 0.03%, 0.02%, 0.01%, or0.001% and can be undetectable by routine ¹¹⁹Sn NMR analysis, such asutilizing a JEOL ECZ 400 with a residence time in the NMR of about 1 hto about 10 h for quantitative data acquisition. Thus, in a furtheraspect, the invention provides the compound of Formula (A), which isuseful as an intermediate in the synthesis of Formula (I).

In one embodiment, the compound of Formula (A) is added as a slurry inhydrocarbon solvent to a slurry of lithium dimethylamide in hydrocarbonsolvent.

In one embodiment, the lithium dimethylamide is freshly prepared fromdimethylamine and an alkyl lithium.

In similar fashion, the corresponding iodo substituted tin compounds ofFormula (A-b) and bromo substituted tin compounds of Formula (A-c) canbe prepared and isolated:

and

Thus, the compounds of Formula (A-a), (A-b), and (A-c) would also beuseful as intermediates in the synthesis of high-puritytris(dimethylamido)isopropyl tin and form another aspect of theinvention.

Accordingly, in a further aspect, the invention provides a process forpreparing a composition comprising a compound of Formula (I-a):

which comprises contacting a compound of Formula (A-a):

with lithium dimethylamide. Furthermore, the invention also provides aprocess for preparing a composition comprising a compound of Formula(I-d):

which comprises contacting a compound of Formula (A-d):

with lithium dimethylamide.

In the processes of the invention, the lithium dimethylamide will eitherbe a solution or a slurry, depending on the solvent or medium utilized;for example, with tetrahydrofuran, the lithium dimethylamide willgenerally be a solution and in hydrocarbons, it would generally be inthe form of a slurry. In one embodiment, the compound of Formula (A-a)is in a slurry with a hydrocarbon solvent, such as hexane. In anotherembodiment, the compound of Formula (A-a) is dissolved in an ethersolvent, such as tetrahydrofuran.

In general, the lithium dimethylamide is present in a molar excess,i.e., of at least about 3 molar equivalents of lithium dimethylamiderelative to 1 molar equivalent of the compound of Formula (A-a) in orderto fully react with the three chlorine atoms on the compound of Formula(A-a). In one embodiment, about 3 to 3.2 equivalents of lithiumdimethylamide is utilized, relative to the compound of Formula (A). Whenpreparing the lithium dimethylamide, it may be advantageous to have amolar excess of dimethyl amine present, for example at least about 1.05molar equivalents of dimethylamine (relative to the alkyl lithiumstarting material, for example n-butyl lithium).

In one embodiment, the composition comprises less than about 0.5% molepercent of impurities, wherein said impurities are comprised ofbis(dimethylamido)diisopropyl tin.

The precursors for the preparation of the compounds of Formula (A-b) and(A-c) can be prepared from the corresponding isopropyl trihalo tincompounds according to the following scheme:

wherein X is bromo or iodo. Instead of a molar excess of iodine orbromine (e.g., approximately 3.5), mono iodo chloride or mono iodobromide can be utilized, as described, for example in (i) Mesubi, M. A.;Afolabi, M. O.; Falase, K. O. Halogen Cleavage ofCyanomethyltriphenylstannane. Inorg. Nucl. Chem. Lett. 1976, 12,469-474, https://doi.org/10.1016/0020-1650(76)80148-1; (ii) Bullard, R.H.; Robinson, W. B. Methylphenylstannanes. J. Am. Chem. Soc. 1927, 49,1368-1373, https://doi.org/10.1021/ja01404a030; (iii) Shekouhian, M.Hassan. Organotin Compound—a Mechanistic Approach for Their Synthesis.J. Recent Adv. Appl. Sci. 1988, 3, 483-486; (iv) Bhattacharya, S. N.;Husain, Ishrat. Reactions of Tin-Naphthyl Bond with Halogens andPseudohalogens. Indian J. Chem. Sect. Inorg. Phys. Theor. Anal. 1981,20A, 1119-1121; and (v) Bhattacharya, S. N.; Raj, P.; Singh, Meenu.Studies on Synthetic and Structural Aspects of Some New Unsymmetric andAsymmetric Organotin(IV) Halides, Pseudohalides and Carboxylates andTheir Complex Anions. Indian J. Chem. Sect. Inorg. Phys. Theor. Anal.1979, 18A, 231-235.)

Thus, as with the corresponding isopropyl tin trichloride, the compoundsof Formula

wherein X is bromo or iodo, can be contacted with 2.0, 4.0, or up to 6.0molar equivalents of dimethylamine, to ensure the formation of the Lewisbase adduct (such as the compounds of Formulae (A-b) and (A-c)),followed by removal of solvent in vacuo to afford the compounds incrystalline form. Accordingly, in a further embodiment, the inventionprovides the compounds of Formulae (A-a), (A-b), and (A-c) incrystalline form. In one embodiment, the crystalline form of thecompound of Formula (A-a) is as set forth in FIG. 1 .

In a further aspect, the invention provides a process for preparingcompounds of Formula R¹SnX₃, wherein X is chloro or bromo and R¹ ischosen from a C₁-C₅ alkyl group, by reacting a compound of the FormulaR¹SnR⁴ ₃ with a mono iodo chloride or bromide respectively, wherein R⁴is chosen from aryl, C₂-C₈ alkenyl, and C₂-C₈ alkynyl, and thusproviding the corresponding isopropyl tin trihalide and iodobenzene. Inthis regard, aryl includes aromatic carbocyclic rings such as phenyl andnapthyl, etc., optionally substituted by C₁-C₆ alkyl, halo, nitro,cyano, C₁-C₆ alkoxy, C₁-C₆ alkylamino, and C₁-C₆ dialkylamino. The C₂-C₈alkenyl and C₂-C₈ alkynyl groups are understood to denote two to eightcarbon hydrocarbons with at least one double bond or triple bond,respectively, and the point of attachment may be to the carbon with thedouble or triple bond, or one of the other carbons in the chain.

In another aspect, the invention provides a process for preparing acompound of Formula R¹SnX₃, wherein X is chloro, bromo, or iodo and R¹is chosen from a C₁-C₅ alkyl group, which comprises contacting acompound of Formula R¹SnR² ₃ with a compound of the Formula SnX₄,wherein R² is chosen from aryl or C₂-C₈ alkenyl.

EXAMPLES Example 1 Synthesis and Isolation of the Bis-dimethylamineLewis Base Adduct of Isopropyl Tin Trichloride

A 100 mL round bottom flask with a gas/vac inlet sidearm adapter wasequipped with a 7 mm tubing adapter. The flask was charged withisopropyl tin trichloride (11.0 g, 41.02 mmol) followed by 60 mLanhydrous hexanes, sealed, and transferred out of the glovebox. Theflask was cooled in an ice bath, and dimethylamine (9.00 g, 199.6 mmol)was slowly bubbled into the solution over 48 minutes via ¼″ PFA tubing.When the addition was complete, a white solid precipitate was observed.The mixture was allowed to warm to ambient temperature and stirred for 2h; it was then filtered and dried in-vacuo to give 12.88 g (86.9%) ofthe desired product as a white solid. Slow evaporation of hexanes fromthe filtrates gave colorless crystals of iPrSnCl₃(HN(CH₃)₂)₂.

¹H NMR (400 MHz, CDCl₃, 298K): δ 3.41 (s, 2H), 2.79 (s, 12H), 2.29(sept, 1H), 1.45 (d, 6H) ppm. ¹³C {¹H} NMR (100 MHz, CDCl₃ 289K): δ45.36, 39.60, 22.38 ppm. ¹¹⁹Sn {¹H} NMR (149 MHz CDCl₃, 298K): δ −405.8ppm.

Example 2 Synthesis and Isolation of the Bis-Dimethylamine Lewis BaseAdduct of Isopropyl Tin Triiodiide

A 100 mL round bottom flask with a gas/vac inlet sidearm adapterequipped with a 7 mm tubing adapter can be charged with isopropyl tintriiodide (10.0 g, 18.43 mmol) followed by 60 mL anhydrous hexanes,sealed, and transferred out of a glovebox. The flask can be cooled in anice bath, and dimethylamine (2.50 g, 55.3 mmol) can be slowly bubbledinto the solution via ¼″ PFA tubing. When the addition is complete, awhite solid precipitate would be observed. The mixture can then beallowed to warm to ambient temperature and stirred for 2 h, filtered anddried in-vacuo to give the expected desired product.

Example 3 Synthesis and Isolation of the Bis-Dimethylamine Lewis BaseAdduct of Isopropyl Tin Tribromide)

A 100 mL round bottom flask with a gas/vac inlet sidearm adapterequipped with a 7 mm tubing adapter can be charged with isopropyl tintribromide (10.0 g, 24.90 mmol) followed by 60 mL anhydrous hexanes,sealed, and transferred out of the glovebox. The flask can be cooled inan ice bath, and dimethylamine (3.37 g, 74.7 mmol) can be slowly bubbledinto the solution via ¼″ PFA tubing. When the addition is complete, awhite solid precipitate would be observed. The mixture can then beallowed to warm to ambient temperature and stirred for 2 h, filtered anddried in-vacuo to give the expected desired product.

Example 4

In an inert atmosphere glovebox a 100 mL round bottom flask with athermowell was equipped with PTFE boiling chips, 50.0 g (127.1 mmol)isopropyltriphenyltin and 99.3 g (381.2 mmol) tin(IV)chloride. A largeexotherm was noted, and when the mixture had cooled to ambienttemperature, the flask was attached to a distillation assembly thatconsisted of a 12″ silvered, vacuum jacketed column packed with 0.16 in²stainless steel Pro-Pak®, a variable reflux distillation head with apressure equalizing arm, and a 100 mL round bottom receiving flask witha gas/vacuum inlet sidearm. The reaction mixture was heated to 120° C.for 3 hours and then distilled at 100 mtorr with the head temperatureranging from 29 to 45° C. with an average head temperature of 36° C. Afirst fraction consisting of 8.24 g (99.9% pure by ¹¹⁹Sn NMR) and asecond fraction consisting of 24.6 g (99.6% pure by ¹¹⁹Sn NMR) werecollected for a combined yield of 32.8 g (96%, 99.7% pure).

¹ H NMR (400 MHz, CDCl₃, 298K): δ 1.61 (sept, 1H) 1.38 (d, 6H) ppm. ¹³C{¹H} NMR (100 MHz, CDCl₃ 289K): δ 40.91, 19.68 ppm. ¹¹⁹Sn {¹H} NMR (149MHz Neat, 298K): δ −12.3 ppm.

Examples A Through I Synthesis of Tris(dimethylamido)isopropyl Tin

The title compound was synthesized according to the following procedureswith Table 1A and 1B below outlining multiple experiments where certainparameters were varied.

Procedure for Examples A and B

A 100 mL round bottom flask with a gas/vacuum inlet sidearm was chargedwith lithium dimethylamide (4.26 g, 83.5 mmol) and 36 mL hexane. A 5 mLsyringe with a stopcock valve was charged with isopropyltin trichloride(7.00 g, 26.1 mmol) and any additives listed in Table 1A below. Theslurry of lithium dimethylamide was cooled to −65° C., and theisopropyltin trichloride was added in a dropwise fashion over 10minutes. Only a very small exotherm was observed, and the mixture wasallowed to warm to ambient temperature. The reaction mixture was allowedto stir for 36 hours at ambient temperature and was then filteredthrough a celite bed and stripped of all volatiles in-vacuo. The crudeproduct was purified via a short path distillation under reducedpressure to give iPrSn(NMe₂)₃ in 55% yield with 0.8% iPr₂Sn(NMe₂)₂impurity as determined by ¹¹⁹Sn NMR.

¹ H NMR (400 MHz, d₆-benzene, 298K): δ 2.83 (s, 18H), 1.63 (sept, 1H),1.27 (d, 6H) ppm. ¹³C {¹H} NMR (100 MHz, d₆-benzene, 289K): δ 43.6,21.2, 14.9 ppm. ¹¹⁹Sn {¹H} NMR (149 MHz Neat, 298K): δ −64.3 ppm.

Procedure for Examples C, D, F, and H

A 250 mL 3-neck round bottom flask equipped with a PTFE coated stir eggwas charged with butyllithium (23.7 mL, 59.4 mmol), diluted with 25 mLanhydrous hexanes, and fitted with a 7 mm tubing adapter, a 7 mm valvedsidearm tubing adapter, and gas/vac inlet adapter. The flask was cooleddown to 2° C. in an ice bath, a condenser was fitted between the flaskand gas/vac inlet adapter, and dimethylamine (6.20 g, 138 mmol, 6.94 eq)was slowly bubbled in via ¼″ PFA tubing. The reaction mixture was cooleddown to approximately −10° C., and a solution of isopropyltintrichloride(5.31 g, 19.8 mmol) diluted to 29 mL with hexanes was added slowly viasyringe pump over 47 minutes (0.61 mL/min). The reaction mixture wasthen allowed to warm to ambient temperature over 20 minutes and stirredfor 1 hour at ambient temperature. The reaction mixture was transferredinto the glovebox and filtered over a bed of celite through a mediumporosity fitted funnel. The residue was washed with 10 mL anhydroushexanes and the solvent was stripped from the filtrates under fullvacuum. The crude yield was 5.427 g (93%) with no detectable amount ofiPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample. The crude product wasdistilled under reduced pressure (50 mtorr at pump) to give 3.929 g(67%) of colorless product with 0.02% iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR.

Procedure for Example E

A 100 mL round bottom flask equipped with a PTFE coated stir egg wascharged with butyllithium (23.0 mL, 57.4 mmol), diluted with 25 mLanhydrous hexanes and fitted with a valved sidearm tubing adapter. Theflask was cooled down to 2° C. in an ice bath, and dimethylamine (5.10g, 113 mmol, 5.72 eq) was slowly bubbled in via ¼″ PTFE tubing at a rateslow enough to keep the reaction temperature under 20° C. The reactionmixture was then allowed to stir overnight at ambient temperature andduring this time all the volatiles present in the reaction mixtureevaporated out via a nitrogen bubbler connected to the flask. Thereaction mixture was diluted with 50 mL of hexanes, cooled in a brinebath to about −10° C. and a solution of isopropyltintrichloride (5.30 g,19.7 mmol) diluted to 26 mL with hexanes was added slowly via syringepump over 43 minutes (0.605 mL/min). The reaction mixture was thenallowed to warm slowly to ambient temperature, stirred for 30 minutes,and then transferred into the glovebox and stirred for 60 h. Thereaction mixture was filtered over a bed of celite and washed with 15 mLof hexanes. The filtrates were stripped of volatiles under reducedpressure to give 4.73 g crude (82%) off-white oil which contained 1.05%iPr₂Sn(NMe₂)₂ as determined by ¹¹⁹Sn NMR of a neat sample. The materialwas then distilled under reduced pressure in a short path distillationapparatus to give 4.019 g (69%) of colorless oil as the product with1.45% iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample.

Procedure for Example G

A 250 mL 3-neck round bottom flask equipped with a PTFE coated stir eggwas charged with lithium dimethylamide (3.38 g, 63.3 mmol), diluted with50 mL anhydrous hexanes and fitted with two stoppers and a valvedsidearm 7 mm tubing adapter. The flask was transferred out to the hoodwhere, under nitrogen purge, the stoppers were swapped out for a PTFEthermocouple adapter with PTFE coated thermocouple and a condenser witha gas/vac inlet valve on top. The flask was cooled down to about −10° C.in an icy brine bath and dimethylamine (2.9 g, 64 mmol, 3.24 eq) wasslowly bubbled in via ¼″ PTFE tubing over a 16-minute span (0.18 g/min).The reaction mixture (still at approximately −10° C.) was treated with asolution of isopropyl tin trichloride (5.32 g, 19.8 mmol) diluted to 23mL with anhydrous hexanes over a 46 minute span. This was then allowedto slowly warm to ambient temperature overnight. The reaction mixturewas filtered over a celite bed and washed with 15 mL hexanes. Thefiltrates were stripped of volatiles under reduced pressure to give 4.86g crude (84%) off-white oil which contained 0.5% iPr₂Sn(NMe₂)₂ asdetermined by ¹¹⁹Sn NMR of a neat sample. The material was thendistilled under reduced pressure in a short path distillation apparatusto give 3.277 g (56%) of colorless oil as the product with 0.75%iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample.

Procedure for Example I

A 250 mL 3-neck round bottom flask equipped with a PTFE coated stir eggwas charged with butyllithium (20.0 mL, 50.0 mmol), diluted with 25 mLanhydrous hexanes and fitted with a 7 mm tubing adapter, a 7 mm valvedsidearm tubing adapter, and gas/vac inlet adapter. The flask was cooleddown to −4° C. in a brine bath, and dimethylamine (5.11 g, 113 mmol,6.77 eq) was slowly bubbled in via ¼″ PTFE tubing over a 26-minute span(approximately 0.20 g/min). The reaction mixture was then stripped ofvolatiles under reduced pressure while keeping the reaction mixturebelow 8° C. When the reaction mixture had been concentrated down to athick paste, the reaction mixture was diluted with 50 mL of anhydroushexanes and cooled down to about −10° C. in a brine bath to prepare forthe addition of the iPrSnCl₃(HNMe₂)₂ slurry. A 100 mL round bottom flaskwith a gas/vac inlet sidearm and a 7 mm tubing adapter was charged withiPrSnCl₃(HNMe₂)₂ (6.00 g, 16.7 mmol) in 30 mL hexanes and equipped witha stir egg. The two flasks were connected via ¼″ PTFE tubing, and theiPrSnCl₃(HNMe₂)₂ slurry was transferred over in two aliquots. Themajority of the residual white solid remaining in the 100 mL flask wasrinsed over with an additional 25 mL anhydrous hexanes and an aliquot ofthe reaction mixture was transferred to and from the 100 mL flask tocomplete the rinse process and ensure complete mixing. The reactionmixture was then allowed to warm up slowly overnight in the brine bath.The reaction mixture which was a slurry of white solid in colorlesssolution was transferred into the glovebox, filtered over a 1 cm bed ofcelite, and rinsed with 10 mL anhydrous hexanes. The solvent and othervolatiles were removed from the filtrates in-vacuo and then massed,yielding 4.310 g crude product (87%) which contained a sub-detectionlimit amount of iPr₂Sn(NMe₂)₂ as determined by ¹¹⁹Sn NMR of a neatsample. The material was then distilled under reduced pressure in ashort path distillation apparatus to give 3.541 g (72% yield) ofcolorless oil as the product with 0.03% iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of aneat sample.

Example K 25.0 g Scale Synthesis of Tris(dimethylamido)isopropyl Tin(Magnetically Stirred)

A 500 mL 3-neck round bottom flask equipped with a PTFE coated stir eggwas charged with butyllithium (107.5 mL, 293.6 mmol) which was dilutedwith hexane (24.51 mL, 186.4 mmol). The flask was fitted with a stopper.gas/vac inlet adapter, and a valved Chemglass 7 mm tubing adapter. Theflask was cooled in a brine bath, and a nitrogen flushed condenser wasplaced unto the flask in the place of the gas/vac inlet adapter.Dimethylamine (30.03 g, 0.661 moles, 7.14 eq) was then slowly bubbledinto the reaction mixture. The resulting slurry was cooled down toapproximately −9° C., and a solution of trichloro(propan-2-yl)stannane(25.00 g, 93.23 mmol) in hexane (122.6 mL, 932.3 mmol) (total volume 135mL) was added via 250 mL addition funnel over 51 minutes. When theaddition was complete, the reaction mixture was allowed to warm toambient temperature and stir for 16 hours. The reaction mixture was thenfiltered over a 2 cm celite bed on a medium porosity filter funnel. Thefilter cake was washed with hexane (24.51 mL, 186.4 mmol) and thecombined filtrates were stripped of solvent under reduced pressure (50mtorr at pump). The yellow oil was transferred to a pre-tared vial andyielded a mass of 19.435 g (70.9%) crude product. The crude product wasdistilled in a short path distillation apparatus under full vacuum togive 16.945 g of slightly yellow oil (61.8% yield). The distilledproduct was analyzed by ¹¹⁹Sn, ¹H, and ¹³C NMR which indicated that0.07% iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample.

Example L 125.0 g Scale Synthesis of Tris(dimethylamido)isopropyl Tin(Mechanically Stirred)

A 3-liter round bottom flask with a mechanical stirrer assembly wascharged with butyllithium (540.0 mL, 1474 mmol) and hexane (525 mL) andthen cooled in a brine bath. Dimethylamine (120.3 g, 2.67 moles, 5.72eq) was bubbled through the cold butyllithium solution over 273 minutesto form a thick white slurry. To this slurry, still cooled in a brinebath, a solution of isopropyltin trichloride (125.00 g, 466.1 mmol) inhexane (610 mL) was added over 52 minutes. The reaction mixture was thenfiltered over a 2 cm bed of celite in a medium porosity filter funnelinto a 2 L round bottom flask and the residual salts were washed withhexane (125 mL). The combined filtrates were then stripped of solventand other volatiles in-vacuo to give 126.8 g (92.6%) crude product. Thecrude product was then filtered through a medium porosity polyethylenefilter funnel to remove the majority of the solids present. The filteredproduct was transferred into a clean 250 mL flask and distilled at 100mtorr to give 116.66 g (85.1%) distilled product with no detectableamount of iPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample.

Example M

A 3-liter round bottom flask with a mechanical stirrer assembly wascharged with 2.74M butyllithium (400 mL, 1096 mmol) and hexane (400 mL)and then cooled in an isopropanol/ice bath. Dimethylamine (66.3 g, 4.224moles) was bubbled through the cold butyllithium solution to form athick white slurry. The lithium dimethylamide reaction mixture was thendiluted with 871 mL anhydrous tetrahydrofuran to form a less viscous butstill inhomogeneous reaction mixture. To this cooled slurry was addedadditional dimethylamine (66.0 g, 4.204 moles) to give a homogeneoussolution. To this solution, still cooled in an isopropanol/water bath,was added a 750 mL solution of isopropyltin trichloridebis(dimethylamine) (125.00 g, 348 mmol) in anhydrous tetrahydrofuranover 199 minutes with the internal reaction temperature between −18° C.and −13° C. The reaction mixture was allowed to slowly warm to ambienttemperature over 18 hours. The reaction mixture was stripped of solventand other volatiles in-vacuo, diluted with 250 mL anhydrous hexanes,filtered through a medium porosity fritted funnel, then washed with anadditional 250 mL aliquot of anhydrous hexanes. The combined filtrateswere then stripped of hexanes and other volatiles in-vacuo to give 101.1g (99%) crude product. The crude product was distilled at 70-100 mtorrto give 88.8 g (87%) distilled product with no detectable amount ofiPr₂Sn(NMe₂)₂ by ¹¹⁹Sn NMR of a neat sample.

TABLE 1 A Process variables for tris(dimethylamido)isopropyl tinsynthesis Tin Xs Tin starting Equivs of equivs of Equivs of LiN(CH₃)₂starting material DMA* dimethyl- LiN(CH₃)₂ synthesis material additionto Tin amine to tin to tin reaction addition min LiNMe₂ starting TinStarting starting starting time rate temp Ex Source material Material***material material (hours) (mL/min) (° C.) A Comm 0 iPrSnCl₃** 0   3.20NA  0.40 −65 B Comm 0 iPrSnCl₃ 0   2.97 NA  0.67 −10 C Synth. 6.51iPrSnCl₃  3.14 3.37 16    0.56 −65 D Synth. 4.63 iPrSnCl₃  1.46 3.1817    0.56 −67 E Synth. 5.72 iPrSnCl₃  2.55 3.18 16    0.60 −10 F Synth.6.70 iPrSnCl₃  3.54 3.16  0.25  0.54 −13 G Comm 3.24 iPrSnCl₃  3.24 3.34NA  0.50 −12 H Synth. 6.94 iPrSnCl₃  3.77 3.17  0.25  0.62 −10 I Synth.6.77***** iPrSnCl₃ ·  3.51 3.26 0.5 NA −9.8 (HN(CH₃)₂)₂ J Comm 0iPrSnCl₃ 0   3.19 NA  0.02 −73 K Synth. 7.14 iPrSnCl₃  4.00 3.15  0.35 2.65 −9.4 L Synth. 5.72 iPrSnCl₃  2.56 3.16  0.40 11.92 −8.8 *DMA =dimethylamine **isopropyl tin trichloride ***In the case of Examples Athrough G, the tin starting material was prepared via iPr₄Sn/SnCl₄redistribution reaction; in the case of example H, the tin startingmaterial was prepared via iPrSn(phenyl)₃ redistribution reaction; and inthe case of Example I, the tin starting material was prepared viaiPrSn(phenyl)₃ redistribution, followed by reaction with excessdimethylamine and isolation of the Lewis base adduct of formula (A).****In the case of Examples A, B, and G, the LiNMe2 was purchasedcommercially as a dry solid and used as received. In Example E, theLiNMe2 was synthesized but all volatiles including any excessdimethylamine were evaporated away as it sat over a 16-hour period.*****In Example I, the volatiles (excess DMA and hexanes) were strippedaway in vacuo so that no excess dimethylamine remained. ******In ExampleB, triethylamine was a synthesis additive in the preparation of theisopropyl(tris)dimethylamine tin; in all other examples, no synthesisadditive was used.

TABLE 1 B Process Variables (continued) Tin Tin Distilled startingstarting iPrSn(N(CH₃)₂)₃ material material iPrSn(N(CH₃)₂)₃ Distilled %of addition addition synthesis iPrSn(N(CH₃)₂)₃ iPr₂Sn(N(CH₃)₂ min tempmax temp reaction time Distilled purity by impurity by Ex (° C.) (° C.)(hours) (% yield) ¹¹⁹Sn NMR ¹¹⁹Sn NMR A −65 23 36 55 97.17 0.77 B −10 2396 NA NA NA C −65 −65 36 41 99.6 0.07 D −67 −65 24 75 99.6 0.17 E −10 060 69 97.8 1.45 F −13 −2 16 78 99.7 0.1 G −12 −8 22 56 98.15 0.75 H −10−4.9 1 67 99.4 0.02 I −9.8 4.7 18 72 99.64 0.03 J −73 −67.4 16 64 97.351.62 K −9.4 1.3 16 61.8 99.69 0.07 L −8.8 0.9 19 85.1 99.94 0.00

Example J (Comparative Example Reproduction of Example 1 of WO2017/066319)

A 100 mL round bottom flask was charged with lithium dimethylamide (3.03g, 59.5 mmol, Sigma Aldrich) and 25 mL hexane. The flask was equippedwith a PTFE coated stir egg and a thermocouple/adapter, then cooled in adry ice/isopropanol bath (−73° C. internal temperature). To this slurrywas added trichloro(propan-2-yl)stannane (5.00 g, 18.6 mmol) via syringeover 122 minutes via syringe pump. The reaction mixture was then allowedto warm up to ambient temperature and stir for 16 h. The reactionmixture was filtered over a celite bed on a medium porosity glass frit.The filter cake was washed with 25 mL anhydrous hexanes and thefiltrates stripped of volatiles under full vacuum. The crude product wasdistilled under full vacuum to give 3.52 g (64.4%) of a colorless oil.The ¹¹⁹Sn NMR spectrum indicated that roughly 1.6% iPr₂Sn(NMe₂)₂ waspresent.

Preparation 1—Synthesis of Isopropyl-SnCl₃ from Isopropyl-Sn(phenyl)₃and SnCl₄

A 2, 3-neck distillation flask with a thermocouple was charged with 753g (1.915 moles) isopropyltriphenyl tin and fitted to an 8″ vigreauxcolumn distillation assembly. A 1 L flask was fitted to the distillationoutlet. The flask containing the isopropyltriphenyltin was charged with1.000 g tin(IV) chloride (3.838 moles, 2 eq., Sigma Aldrich) over a spanof approximately two hours with a moderate exotherm observed. Theisopropyl tin trichloride was then distilled at 1 torr between 65° C.and 75° C. with the head temperature rising sharply to about 1.00° C. atthe conclusion of the distillation. The product (588 g) was found to bea mixture of PhSnCl₃ (15 mole %) and iPrSnCl₃ (85 mole %) with thedistillation pot material consisting of 55 mole % Ph₂SnCl₂ and 45 mole %PhSnCl₃ by ¹¹⁹Sn NMR. The yield of iPrSnCl₃ calculated from the relativeNMR integrations was 493 g (96% yield). The mixture of iPrSnCl₃ andPhSnCl₃ was further distilled using a 1′ column packed with stainlesssteel 0.16 in² Pro-Pak® at 50-100 mtorr with a head temperature of40-43° C. to give 461 g (90%) iPrSnCl₃ with 99.9% purity by ¹¹⁹Sn NMR.

NMR (400 MHz, CDCl₃, 298K): d 1.61 (sept, 1H), 1.38 (d, 6H) ppm. ¹³C{¹H} NMR (100 MHz, CDCl₃ 289K): d 40.9, 19.7 ppm. ¹¹⁹Sn {¹H} NMR (149MHz CDCl₃, 298K): d −5.9 ppm.

Preparation 2—Synthesis of Isopropyl-SnCl₃ from (Phenyl)₃Sn-isopropyland ICl

A 100 mL round bottom flask was equipped with a PTFE coated stir egg,charged with isopropyltriphenyl tin (10.00 g, 25.43 mmol), 50 mLanhydrous hexanes and iodine monochloride (12.42 g, 76.54 mmol) wasadded in a dropwise fashion with stirring. The temperature rose from 22°C. to 71° C. over the course of the 10 minute addition. The reactionmixture was then allowed to stir 18 h at ambient temperature. The 119SnNMR of a reaction aliquot indicated that a small amount of iPrSnPhCl₂was present. The reaction mixture was treated with iodine monochloride(2.063 g, 12.71 mmol) (an additional 0.5 eq) and then allowed to stir atambient temperature for 30 minutes. The solvent was then removed under a10 torr vacuum to give crude product (22.439 g, a mixture of the desiredproduct and iodobenzene). The product was then distilled using a 6″14/20 distillation column packed with stainless steel 0.16 in² Pro-Pak®to give three fractions: Fraction 1—8.86 g, 8.4 mole % iPrSnCl₃,Fraction 2—7.08 g, 36.9 mole % iPrSnCl₃, Fraction 3—4.86 g, 93.8 mole %iPrSnCl₃. Overall, the recovery of the iPrSnCl₃ was quantitative.

Preparation 3—Synthesis of IsopropylSnI₃ from Ph₃Sn-Isopropyl and I₂

A 40 m vial was charged with isopropyl triphenyltin (5.00 g, 12.7 mmol)and 20 mL of toluene. Iodine (10.2 g, 40.0 mmol) was slowly added inseveral portions with an exotherm observed after each addition. Theresulting deep red mixture was then heated 16 h at 90° C. The resultingsolution was then distilled in-vacuo in a short path apparatus, first toremove the iodobenzene by-product, and then to distill the product(100-105° C. head temp, 200-500 mtorr) as a yellow oil in 94% yield.

¹H NMR (400 MHz, benzene-d₆, 298K): d 1.78 (sept, 1H), 0.61 (d, 6H) ppm.¹³C {¹H} NMR (100 MHz, benzene-d₆, 289K): d 37.6, 19.8 ppm. 119 Sn {¹H}NMR (149 MHz benzene-d₆, 298K): d −434 ppm.

EtSnCl₃—Synthesis and Purification

Ph₃SnEt (637.8 g, 1.68 mol) was loaded into a 4-neck 2 L roundbottomflask equipped with a magnetic stir bar, thermocouple, and nitrogeninlet adapter. In a nitrogen-filled glovebox, SnCl₄ (916 g, 3.52 mol)was placed in a 500 mL addition funnel, which was then removed from theglovebox and attached to the 2 L roundbottom flask. The apparatus wasplaced under N₂, and the SnCl₄ was added slowly over 8 hours directly tothe solid Ph₃SnEt. The reaction mixture was heated to 115° C. for 1 hourand then distilled using a jacketed 8″ vigreaux distillation column at 1torr between 67° C. and 69° C. A 2-3 mL forecut was collected and thedistillation was stopped when the head temperature reached 78° C. Asecond distillation was carried out using an 8″ column packed with glassraschig rings at 1 torr with a head temperature of about 64° C. to giveEtSnCl₃ as a colorless liquid (327.16 g, 108 mol, 76.7% yield) in >99.0%purity. ¹H-NMR (400 MHz, C₆D₆, 298K): 1.43 (t, 3H); 2.27 (q, 2H) ppm;¹¹⁹Sn NMR (149 MHz, 298K): 2.03 ppm.

EtSnCl₃(HNMe₂)₂—Synthesis and Characterization

A 5 L 3-neck jacketed flask equipped with an overhead stirrer, gas inletadapter, and thermocouple was brought into a nitrogen-filled glovebox.EtSnCl₃ (391 g, 1.53 mol) was placed in the flask and diluted with 3 Lof hexanes. HNMe₂ was bubbled into the reaction flask at a rate of about1.0 g/min. Over the course of 4 hours HNMe₂ (149.3 g, 3.30 mol) wasadded with an exotherm of about 20° C., resulting in the formation of awhite precipitate. The reaction mixture was stirred at room temperaturefor about 18 h, filtered through a medium porosity frit, washed with 500mL hexanes, and dried in-vacuo to give 477 g of a slightly tacky whitesolid (90.7%) in >99.0% purity. ¹H-NMR (400 MHz, CDCl₃, 298K): 1.28 (t,3H); 1.75 (q, 2H); 2.77 (s, 12H); 3.44 (s, 2H) ppm; ¹³C-NMR (100 MHz,CDCl₃, 298K): 12.75, 29.61, 38.88 ppm; ¹¹⁹Sn-NMR (149 MHz CDCl₃, 298K):−394.5 ppm.

EtSn(NMe₂)₃—Synthesis and Purification

A 12 L 4-neck flask with a mechanical stirrer assembly was charge withnBuLi (2.5M, 1.73 L, 4.34 mol) which was diluted with 3 L of hexanes.The nBuLi solution was then cooled to an internal temperature of 0° C.using an IPA/liquid N₂ bath. Dimethylamine gas was bubbled into thereaction at a rate of about 1 g/min over the course of 5 hours with aninternal reaction temperature less than 3° C. forming a viscous whitemixture. The LiNMe₂ reaction mixture was warmed to room temperature andallowed to stir for about 72 hours. The LiNMe₂ mixture was cooled toabout −2° C. using the IPA/N₂ bath and was then treated with a solutionof EtSnCl₃(HNMe₂)₂ (477 g, 1.38 mol) in 3 L dimethoxyethane over thecourse of 2.5 hours in the dark (all subsequent steps performed in thedark as well) with an internal reaction temperature from about 1-2° C.resulting in a slightly yellow solution which was stirred for about 18 hat ambient temperature. The yellowish reaction mixture was stripped ofsolvent and other volatiles in-vacuo to give a tacky off-white/yellowsolid which was slurried in 3 L hexanes and filtered through a mediumporosity frit. The filtrates were then stripped of hexanes and othervolatiles in-vacuo to give an orange oil as the crude product. The crudeproduct was distilled using a 10″ Vigreux column over a pressure rangeof 200 to 500 mtorr and a head temperature from 28 to 35° C. A 10 mLforecut was discarded and a main fraction of EtSn(NMe₂)₃ was collectedas a colorless liquid (278 g, 0.99 mol, 72% yield) in 99.84% purity.¹H-NMR (400 MHz, C₆D₆, 298K): 0.99 (q, 2H); 1.15 (t, 3H); 2.73 (s, 18H)ppm; ¹³C-NMR (100 MHz, C₆D₆, 298K): 4.32, 10.14, 43.27 ppm; ¹¹⁹Sn-NMR(149 MHz, C₆D₆, 298K): −38.48 ppm.

Crystal Structure Data

As noted above, FIG. 1 is a three-dimensional solid state crystalstructure depiction of iPrSnCl₃(HN(CH₃)₂)₂. The compound was subjectedto x-ray crystallographic analysis and yielded the following data:

TABLE 2 Crystal data and structure refinement for iPrSnCl₃(HN(CH₃)₂)₂.Report date 2020 Dec. 11 Empirical formula C7 H21 Cl3 N2 Sn Molecularformula C7 H21 Cl3 N2 Sn Formula weight 358.30 Temperature 100.0 KWavelength 0.71073 Å Crystal system Monoclinic Space group C 1 2/c 1Unit cell dimensions a = 20.4199(5) Å α = 90°. b = 9.1826(2) Å β =109.1330(10)°. c = 15.8327(4) Å γ = 90°. Volume 2804.76(12) Å3 Z 8Density (calculated) 1.697 Mg/m3 Absorption coefficient 2.361 mm-1F(000) 1424 Crystal size 0.18 × 0.18 × 0.14 mm3 Crystal color, habitcolorless irregular Theta range for data 2.111 to 26.371°. collectionIndex ranges −25 <= h <= 25, −11 <= k <= 11, −19 <= l <= 18 Reflectionscollected 14764 Independent reflections 2873 [R(int) = 0.0397]Completeness to 100.0% theta = 25.242° Absorption correctionSemi-empirical from equivalents Max. and min. 0.4910 and 0.4460transmission Refinement method Full-matrix least-squares on F2Data/restraints/ 2873/0/124 parameters Goodness-of-fit on F2 1.044 FinalR indices R1 = 0.0157, [I>2sigma(I)] wR2 = 0.0385 R indices (all data)R1 = 0.0172, wR2 = 0.0394 Largest diff. peak 0.359 and −0.279 e·Å-3 andhole

In addition, as also noted above, FIG. 2 is a three-dimensional solidstate crystal structure depiction of EtSnCl₃(HN(CH₃)₂)₂. The compoundwas subjected to x-ray crystallographic analysis and yielded thefollowing data:

TABLE 3 Crystal data and structure refinement for EtSnCl₃(HN(CH₃)₂)₂.Report date 2021 Oct. 8 Empirical formula C6 H19 Cl3 N2 Sn Molecularformula C6 H19 Cl3 N2 Sn Formula weight 344.27 Temperature 100.0 KWavelength 0.71073 Å Crystal system Monoclinic Space group P 1 21 1 Unitcell dimensions a = 6.3562(3) Å α = 90°. b = 12.1949(8) Å β =96.019(2)°. c = 8.3133(6) Å γ = 90°. Volume 640.84(7) Å3 Z 2 Density(calculated) 1.784 Mg/m3 Absorption coefficient 2.579 mm-1 F(000) 340Crystal size 0.22 × 0.095 × 0.03 mm3 Crystal color, habit colorlessplate Theta range for data 2.464 to 26.369°. collection Index ranges −7<= h <= 7, −13 <= k <= 15, −10 <= l <= 10 Reflections collected 6343Independent reflections 2404 [R(int) = 0.0192] Completeness to 99.8%theta = 25.242° Absorption correction Semi-empirical from equivalentsMax. and min. 0.4910 and 0.4172 transmission Refinement methodFull-matrix least-squares on F2 Data/restraints/ 2404/1/119 parametersGoodness-of-fit on F2 1.026 Final R indices R1 = 0.0124, [I>2sigma(I)]wR2 = 0.0263 R indices (all data) R1 = 0.0127, wR2 = 0.0264 Absolutestructure −0.004(13) parameter Extinction coefficient 0.0027(6) Largestdiff. peak 0.306 and −0.204 e·Å-3 and hole

ASPECTS

In a first aspect, the invention provides a composition comprising acompound of Formula (I):

wherein each R is independently chosen from a C₁-C₅ alkyl group, and R¹is chosen from a C₁-C₅ alkyl group, and wherein said compositioncomprises less than about 0.5% concentration, by mole, of a compound ofFormula (II):

In a second aspect, the invention provides the composition of the firstaspect, wherein R and R¹ are independently chosen from a C₁-C₃ alkylgroup.

In a third aspect, the invention provides the composition of the firstor second aspects, wherein the compound of Formula (I) istris(dimethyl-amido)isopropyl tin; tris(diethylamido)isopropyl tin;tris(dipropylamido)isopropyl tin; tris(methylethylamido)isopropyl tin;tris(diisopropylamido)isopropyl tin; tris(di-t-butyl-amido)isopropyltin; tris(di-n-butylamido)isopropyl tin;tris(di-sec-butylamido)isopropyl tin; tris(di-neopentylamido)isopropyltin; tris(dimethylamido)methyl tin; tris(diethylamido)methyl tin;tris(di-n-propylamido)methyl tin; tris(methylethylamido)methyl tin;tris(diisopropylamido)methyl tin; tris(di-t-butylamido)methyl tin;tris(di-n-butylamido)methyl tin; tris(di-sec-butylamido)methyl tin;tris(di-neopentylamido)methyl tin; tris(dimethylamido)ethyl tin;tris(diethylamido)ethyl tin; tris(di-n-propylamido)ethyl tin;tris(methylethylamido)ethyl tin; tris(diisopropylamido)ethyl tin;tris(di-t-butylamido)ethyl tin; tris(di-n-butylamido)ethyl tin;tris(di-sec-butylamido)ethyl tin; tris(di-neopentylamido)ethyl tin;tris(dimethylamido)n-propyl tin; tris(diethylamido)n-propyl tin;tris(di-n-propylamido)n-propyl tin; tris(methylethylamido)n-propyl tin;tris(diisopropylamido)n-propyl tin; tris(di-t-butylamido)n-propyl tin;tris(di-n-butylamido)n-propyl tin; tris(di-sec-butylamido)n-propyl tin;tris(di-neopentylamido)n-propyl tin; tris(dimethylamido)n-butyl tin;tris(diethylamido)n-butyl tin; tris(dipropylamido)n-butyl tin;tris(methylethylamido)n-butyl tin; tris(diisopropylamido)n-butyl tin;tris(di-t-butylamido)n-butyl tin; tris(di-n-butylamido)n-butyl tin;tris(di-sec-butylamido)n-butyl tin; or tris(di-neopentylamido)n-butyltin.

In a fourth aspect, the invention provides the composition of any one ofthe first through third aspects, wherein the compound of Formula (I) istris(dimethylamido)isopropyl tin; tris(diethylamido)isopropyl tin;tris(dipropylamido)isopropyl tin; tris(methylethylamido)isopropyl tin;tris(diisopropylamido)isopropyl tin; tris(di-t-butylamido)isopropyl tin;tris(di-n-butylamido)isopropyl tin; tris(di-sec-butylamido)isopropyltin; or tris(di-neopentylamido)isopropyl tin.

In a fifth aspect, the invention provides the composition of any one ofthe first through fourth aspects, wherein the compound of Formula (I) istris(dimethylamido)isopropyl tin, and the compound of Formula (II) isbis(dimethylamido)diisopropyl tin.

In a sixth aspect, the invention provides the composition of any one ofthe first through fifth aspects, wherein the compound of Formula (II) ispresent in a concentration of less than about 0.1% by mole.

In a seventh aspect, the invention provides the composition of any oneof the first through sixth aspects, wherein the compound of Formula (II)is present in a concentration of less than about 0.05% by mole.

In an eighth aspect, the invention provides the composition of any oneof the first through seventh aspects, wherein the compound of Formula(II) is present in a concentration of less than about 0.03% by mole.

In a ninth aspect, the invention provides a process for preparing acomposition comprising a compound of Formula (I):

wherein each R is independently chosen from a C₁-C₅ alkyl group, and R¹is chosen from a C₁-C₅ alkyl group, which comprises combining:

-   -   a) a compound of Formula R¹SnX₃, wherein X is chosen from Cl, I,        and Br,    -   b) a compound of Formula Li(R)₂N, and    -   c) a compound of Formula and R₂NH,        wherein the compound of Formula R₂NH is present in a molar        excess over the compound of Formula R¹SnX₃.

In a tenth aspect, the invention provides the process of the ninthaspect, wherein R and R¹ are independently chosen from a C₁-C₃ alkylgroup.

In an eleventh aspect, the invention provides the process of the ninthor tenth aspects, wherein R¹ is isopropyl and X is chloro.

In a twelfth aspect, the invention provides the process of any one ofthe ninth through eleventh aspects, wherein the compound of Formula (I)is tris(dimethyl-amido)isopropyl tin; tris(diethylamido)isopropyl tin;tris(dipropylamido)isopropyl tin; tris(methylethylamido)isopropyl tin;tris(diisopropylamido)isopropyl tin; tris(di-t-butyl-amido)isopropyltin; tris(di-n-butylamido)isopropyl tin;tris(di-sec-butylamido)isopropyl tin; tris(di-neopentylamido)isopropyltin; tris(dimethylamido)methyl tin; tris(diethylamido)methyl tin;tris(di-n-propylamido)methyl tin; tris(methylethylamido)methyl tin;tris(diisopropylamido)methyl tin; tris(di-t-butylamido)methyl tin;tris(di-n-butylamido)methyl tin; tris(di-sec-butylamido)methyl tin;tris(di-neopentylamido)methyl tin; tris(dimethylamido)ethyl tin;tris(diethylamido)ethyl tin; tris(di-n-propylamido)ethyl tin;tris(methylethylamido)ethyl tin; tris(diisopropylamido)ethyl tin;tris(di-t-butylamido)ethyl tin; tris(di-n-butylamido)ethyl tin;tris(di-sec-butylamido)ethyl tin; tris(di-neopentylamido)ethyl tin;tris(dimethylamido)n-propyl tin; tris(diethylamido)n-propyl tin;tris(di-n-propylamido)n-propyl tin; tris(methylethylamido)n-propyl tin;tris(diisopropylamido)n-propyl tin; tris(di-t-butylamido)n-propyl tin;tris(di-n-butylamido)n-propyl tin; tris(di-sec-butylamido)n-propyl tin;tris(di-neopentylamido)n-propyl tin; tris(dimethylamido)n-butyl tin;tris(diethylamido)n-butyl tin; tris(dipropylamido)n-butyl tin;tris(methylethylamido)n-butyl tin; tris(diisopropylamido)n-butyl tin;tris(di-t-butylamido)n-butyl tin; tris(di-n-butylamido)n-butyl tin;tris(di-sec-butylamido)n-butyl tin; or tris(di-neopentylamido)n-butyltin.

In a thirteenth aspect, the invention provides the process of any one ofthe ninth through twelfth aspects, wherein the compound of Formula (I)is chosen from tris(dimethylamido)isopropyl tin;tris(diethylamido)isopropyl tin; tris(dipropylamido)isopropyl tin;tris(methylethylamido)isopropyl tin; tris(diisopropylamido)isopropyltin; tris(di-t-butylamido)isopropyl tin; tris(di-n-butylamido)isopropyltin; tris(di-sec-butylamido)isopropyl tin; andtris(di-neopentylamido)isopropyl tin.

In a fourteenth aspect, the invention provides the process of any one ofthe ninth through thirteenth aspects, wherein the compound of FormulaR₂NH is dimethylamine and R¹ is isopropyl.

In a fifteenth aspect, the invention provides the process of any one ofthe ninth through fourteenth aspects, wherein the compound of FormulaLi(R)₂N is lithium dimethylamide, the compound of Formula R₂NH isdimethylamine, and the compound of Formula R¹SnX₃ is isopropyl-tintrichloride.

In a sixteenth aspect, the invention provides the process of thefifteenth aspect, wherein the composition comprises less than about 0.5%of bis(dimethylamido)diisopropyl tin.

In a seventeenth aspect, the invention provides the process of thefifteenth or sixteenth aspects, wherein the composition comprises lessthan about 0.1% of bis(dimethylamido)diispropyl tin.

In an eighteenth aspect, the invention provides the process of any oneof the fifteenth through the seventeenth aspects, wherein thecomposition comprises less than about 0.05% ofbis(dimethylamido)diisopropyl tin.

In a nineteenth aspect, the invention provides the process of any one ofthe ninth through eighteenth aspects, wherein the compound of FormulaR₂NH is present in at least about a 0.15 molar equivalents over thecompound of Formula R¹SnX₃.

In a twentieth aspect, the invention provides a process of any of theninth through the nineteenth aspects, wherein the compound of Formula(I) is prepared from a compound of Formula (A):

In a twenty-first aspect, the invention provides a process of thetwentieth aspect, wherein the compound of Formula (A) is prepared by areaction of the compound of Formula R₂NH and a compound of FormulaR¹SnX₃, wherein the compound of Formula R₂NH is in excess of thecompound of Formula R¹SnX₃.

In a twenty-second aspect, the invention provides a process of thetwentieth or twenty-first aspects, wherein the compound of Formula (I)is prepared by reaction of the compound of Formula (A) and the compoundof Formula Li(R)₂N.

In a twenty-third aspect, the invention provides a process of any one ofthe twentieth through twenty-second aspects, wherein the compound ofFormula Li(R)₂N is present in a molar excess of about 3 to about 3.2molar equivalents, relative to the compound of Formula (A).

In a twenty-fourth aspect, the invention provides a process of any oneof the twentieth through twenty-third aspects, wherein the compound ofFormula (I) is a compound of Formula (I-a):

the compound of Formula (A) is a compound of Formula (A-a):

and the compound of Formula Li(R)₂N is lithium dimethylamide.

In a twenty-fifth aspect, the invention provides a process of any one ofthe twentieth through twenty-third aspects, wherein the compound ofFormula (I) is a compound of Formula (I-d):

the compound of Formula (A) is a compound of Formula (A-d):

and the compound of Formula Li(R)₂N is lithium dimethylamide.

In a twenty-sixth aspect, the invention provides a process of any one ofthe twentieth through twenty-fifth aspects, wherein the compound ofFormula R¹SnX₃, wherein X is chloro or bromo and R¹ is chosen from aC₁-C₅ alkyl group, is prepared by reacting a compound of Formula R¹SnR⁴₃ and a mono iodo chloride or bromide respectively, wherein R⁴ is chosenfrom aryl, C₂-C₈ alkenyl, and C₂-C₈ alkynyl.

In a twenty-seventh aspect, the invention provides a process of any oneof the twentieth through twenty-fifth aspects, wherein the compound ofFormula R¹SnX₃, wherein X is chloro, bromo, or iodo and R¹ is chosenfrom a C₁-C₅ alkyl group, is prepared by contacting a compound ofFormula R¹SnR² ₃, wherein R² is chosen from aryl or C₂-C₈ alkenyl, witha compound of Formula SnX₄.

In a twenty-eighth aspect, the invention provides a compound of Formula(A-a):

In a twenty-ninth aspect, the invention provides a compound of thetwenty-eighth aspect in crystalline form as depicted in FIG. 1 .

In a thirtieth aspect, the invention provides a compound of Formula(A-d):

In a thirty-first aspect, the invention provides a compound of thethirtieth aspect in crystalline form as depicted in FIG. 2 .

In a thirty-second aspect, the invention provides a process forpreparing a compound of Formula R¹SnX₃, wherein X is chloro or bromo andR¹ is chosen from a C₁-C₅ alkyl group, which comprises reacting acompound of Formula R¹SnR⁴ ₃ with a mono iodo chloride or bromiderespectively, wherein R⁴ is chosen from aryl, C₂-C₈ alkenyl, and C₂-C₈alkynyl.

In a thirty-third aspect, the invention provides a process for preparinga compound of Formula R¹SnX₃, wherein X is chloro, bromo, or iodo and R¹is chosen from a C₁-C₅ alkyl group, which comprises contacting acompound of Formula R¹SnR² ₃ with a compound of the formula SnX₄,wherein R² is chosen from aryl or C₂-C₈ alkenyl.

Having thus described several illustrative embodiments of the presentdisclosure, those of skill in the art will readily appreciate that yetother embodiments may be made and used within the scope of the claimshereto attached. Numerous advantages of the disclosure covered by thisdocument have been set forth in the foregoing description. It will beunderstood, however, that this disclosure is, in many respects, onlyillustrative. The disclosure's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A process for preparing a composition comprisinga compound of Formula (I):

wherein each R is independently chosen from a C₁-C₅ alkyl group, and R¹is chosen from a C₁-C₅ alkyl group, which comprises combining: a) acompound of Formula R¹SnX₃, wherein X is chosen from Cl, I, and Br, b) acompound of Formula Li(R)₂N, and c) a compound of Formula and R₂NH,wherein the compound of Formula R₂NH is present in a molar excess overthe compound of Formula R¹SnX₃.
 2. The process of claim 1, wherein R andR¹ are independently chosen from a C₁-C₃ alkyl group.
 3. The process ofclaim 1, wherein R¹ is isopropyl and X is chloro.
 4. The process ofclaim 1, wherein the compound of Formula (I) istris(dimethyl-amido)isopropyl tin; tris(diethylamido)isopropyl tin;tris(dipropylamido)isopropyl tin; tris(methylethylamido)isopropyl tin;tris(diisopropylamido)isopropyl tin; tris(di-t-butyl-amido)isopropyltin; tris(di-n-butylamido)isopropyl tin;tris(di-sec-butylamido)isopropyl tin; tris(di-neopentylamido)isopropyltin; tris(dimethylamido)methyl tin; tris(diethylamido)methyl tin;tris(di-n-propylamido)methyl tin; tris(methylethylamido)methyl tin;tris(diisopropylamido)methyl tin; tris(di-t-butylamido)methyl tin;tris(di-n-butylamido)methyl tin; tris(di-sec-butylamido)methyl tin;tris(di-neopentylamido)methyl tin; tris(dimethylamido)ethyl tin;tris(diethylamido)ethyl tin; tris(di-n-propylamido)ethyl tin;tris(methylethylamido)ethyl tin; tris(diisopropylamido)ethyl tin;tris(di-t-butylamido)ethyl tin; tris(di-n-butylamido)ethyl tin;tris(di-sec-butylamido)ethyl tin; tris(di-neopentylamido)ethyl tin;tris(dimethylamido)n-propyl tin; tris(diethylamido)n-propyl tin;tris(di-n-propylamido)n-propyl tin; tris(methylethylamido)n-propyl tin;tris(diisopropylamido)n-propyl tin; tris(di-t-butylamido)n-propyl tin;tris(di-n-butylamido)n-propyl tin; tris(di-sec-butylamido)n-propyl tin;tris(di-neopentylamido)n-propyl tin; tris(dimethylamido)n-butyl tin;tris(diethylamido)n-butyl tin; tris(dipropylamido)n-butyl tin;tris(methylethylamido)n-butyl tin; tris(diisopropylamido)n-butyl tin;tris(di-t-butylamido)n-butyl tin; tris(di-n-butylamido)n-butyl tin;tris(di-sec-butylamido)n-butyl tin; or tris(di-neopentylamido)n-butyltin.
 5. The process of claim 1, wherein the compound of Formula (I) ischosen from tris(dimethylamido)isopropyl tin;tris(diethylamido)isopropyl tin; tris(dipropylamido)isopropyl tin;tris(methylethylamido)isopropyl tin; tris(diisopropylamido)isopropyltin; tris(di-t-butylamido)isopropyl tin; tris(di-n-butylamido)isopropyltin; tris(di-sec-butylamido)isopropyl tin; andtris(di-neopentylamido)isopropyl tin.
 6. The process of claim 1, whereinthe compound of Formula Li(R)₂N is lithium dimethylamide, the compoundof Formula R₂NH is dimethylamine, and the compound of Formula R¹SnX₃ isisopropyl-tin trichloride.
 7. The process of claim 1, wherein thecompound of Formula (I) is prepared from a compound of Formula (A):


8. The process of claim 7, wherein the compound of Formula (A) isprepared by a reaction of the compound of Formula R₂NH and the compoundof Formula R¹SnX₃, wherein the compound of Formula R₂NH is in excess ofthe compound of Formula R¹SnX₃.
 9. The process of claim 7, wherein thecompound of Formula (I) is prepared by reaction of the compound ofFormula (A) and the compound of Formula Li(R)₂N.
 10. The process ofclaim 7, wherein the compound of Formula Li(R)₂N is present in a molarexcess of about 3 to about 3.2 molar equivalents, relative to thecompound of Formula (A).
 11. The process of claim 7, wherein thecompound of Formula (I) is a compound of Formula (I-a):

the compound of Formula (A) is a compound of Formula (A-a):

and the compound of Formula Li(R)₂N is lithium dimethylamide.
 12. Theprocess of claim 7, wherein the compound of Formula (I) is a compound ofFormula (I-d):

the compound of Formula (A) is a compound of Formula (A-d):

and the compound of Formula Li(R)₂N is lithium dimethylamide.
 13. Theprocess of claim 1, wherein, the compound of Formula R¹SnX₃, wherein Xis chloro or bromo and R¹ is chosen from a C₁-C₅ alkyl group, isprepared by reacting a compound of Formula R¹SnR⁴ ₃ and a mono iodochloride or bromide respectively, wherein R⁴ is chosen from aryl, C₂-C₈alkenyl, and C₂-C₈ alkynyl.
 14. The process of claim 1, wherein thecompound of Formula R¹SnX₃, wherein X is chloro, bromo, or iodo and R¹is chosen from a C₁-C₅ alkyl group, is prepared by contacting a compoundof Formula R¹SnR² ₃, wherein R² is chosen from aryl or C₂-C₈ alkenyl,with a compound of Formula SnX₄.